RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Yep. but there's no silver. This is (was) copper-clad aluminum. Mike WM4B _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Kris Kirby Sent: Thursday, October 09, 2008 4:50 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables On Wed, 8 Oct 2008, Mike Besemer (WM4B) wrote: These babies are looking pretty rough, Paul (et al). After one pass with the synthetic steel wool and a wipe with isopropyl alcohol, I can see that the copper plating near the open end of the outer tubes is nearly gone on two of the cans. Have not done the other two yet, but they seem to be in better shape. I'm thinking more and more they're gonna need a refurb, although I can't see how they'd do anything with these, since the don't come apart any further. Or course, silver oxide is conductive, unlike most other oxides. -- Kris Kirby, KE4AHR [EMAIL PROTECTED] mailto:kris%40catonic.us us But remember, with no superpowers comes no responsibility. --rly
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, OK, that makes sense re the 004/005 markings. And OK on the knobs. That really messed with me at first. I thought they were glued or something. It was only when I tried heating one to see if the glue would soften that I found out it was solder! I didn't have any trouble with the top of the inner tube catching on the finger stock when I put them back in, but it was a real close fit getting them in without that happening. On each cavity there were, as I recall, two or three fingers that were sprung inward a little more than the others, possibly having to do with the ends of the two coil springs putting extra pressure on them. Those were the ones I had to watch closely. As long as it hasn't compromised the solder bond of the finger stock in some way, I'm not sure the worn copper plating will do much harm. Of course if the copper plate between the finger stock solder and the inside of the fixed inner tube has deteriorated in any way (which you can't possibly determine by looking), then that would be a serious issue. My guess is it's probably OK. I would just clean them up as best I could and try it. If you can't find someone who knows where the 004 and 005 loops go, I would try an experiment. I would put both 004 on one side of the duplexer, both 005 on the other side. I would then tune it up for high pass on the 004 side (low on the 005) and make a note of the performance measurements (notch depth, insertion loss, VSWR or return loss - measure all parameters on both low and high pass sides of course). Then I would retune it so the 004 side was low pass (and 005 side high pass) and measure the performance again. If there was any difference, I'd go with the configuration that produced the better numbers. If you try this, I would be interested in what you find out. Having said all that, it's also possible the loops were intended to go the way you found them... one 004 and one 005 on each side. That wouldn't be my first guess, but it's possible. It might have something to do with making the impedances look a little nicer or some such... Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I just noticed that what I wrote here was backwards... the 004s had the strap all the way around and the 005s had the wire extension. If I figure out what goes where, I'll let you know. Did you have trouble with the top of the inner loop catching on the fingerstock and tweaking it a bit? I bent a couple of mine, but it tweaked back into place okay. Mike WM4B
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
On Wed, 8 Oct 2008, Mike Besemer (WM4B) wrote: These babies are looking pretty rough, Paul (et al). After one pass with the synthetic steel wool and a wipe with isopropyl alcohol, I can see that the copper plating near the open end of the outer tubes is nearly gone on two of the cans. Have not done the other two yet, but they seem to be in better shape. I'm thinking more and more they're gonna need a refurb, although I can't see how they'd do anything with these, since the don't come apart any further. Or course, silver oxide is conductive, unlike most other oxides. -- Kris Kirby, KE4AHR [EMAIL PROTECTED] But remember, with no superpowers comes no responsibility. --rly
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Thanks Paul. I agree with you on everything you said. One thing is for sure, I can't possibly make matters worse! I finally got to talk to a guy at dbSpectra today. He vaguely remembered the different loops but couldn't remember how they were installed. He was going to try to find some old tech data and send it to me. I haven't seen it yet, but hopefully it's coming. I'll try to take notes and pictures as I go along and send you anything that might be useful for your 'how-to' guide. 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Thursday, October 09, 2008 7:20 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, OK, that makes sense re the 004/005 markings. And OK on the knobs. That really messed with me at first. I thought they were glued or something. It was only when I tried heating one to see if the glue would soften that I found out it was solder! I didn't have any trouble with the top of the inner tube catching on the finger stock when I put them back in, but it was a real close fit getting them in without that happening. On each cavity there were, as I recall, two or three fingers that were sprung inward a little more than the others, possibly having to do with the ends of the two coil springs putting extra pressure on them. Those were the ones I had to watch closely. As long as it hasn't compromised the solder bond of the finger stock in some way, I'm not sure the worn copper plating will do much harm. Of course if the copper plate between the finger stock solder and the inside of the fixed inner tube has deteriorated in any way (which you can't possibly determine by looking), then that would be a serious issue. My guess is it's probably OK. I would just clean them up as best I could and try it. If you can't find someone who knows where the 004 and 005 loops go, I would try an experiment. I would put both 004 on one side of the duplexer, both 005 on the other side. I would then tune it up for high pass on the 004 side (low on the 005) and make a note of the performance measurements (notch depth, insertion loss, VSWR or return loss - measure all parameters on both low and high pass sides of course). Then I would retune it so the 004 side was low pass (and 005 side high pass) and measure the performance again. If there was any difference, I'd go with the configuration that produced the better numbers. If you try this, I would be interested in what you find out. Having said all that, it's also possible the loops were intended to go the way you found them... one 004 and one 005 on each side. That wouldn't be my first guess, but it's possible. It might have something to do with making the impedances look a little nicer or some such... Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I just noticed that what I wrote here was backwards... the 004s had the strap all the way around and the 005s had the wire extension. If I figure out what goes where, I'll let you know. Did you have trouble with the top of the inner loop catching on the fingerstock and tweaking it a bit? I bent a couple of mine, but it tweaked back into place okay. Mike WM4B image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Yep. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 11:35 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Hi Mike, I am a little confused as to how you are coupling the signal generator to the receiver. When you have the tx and rx connected to the duplexer normally and a dummy load on the output T (that would normally feed the antenna line) how are you coupling the signal generator to the receiver? Are you using an isolated T in the receive line to couple the generator in? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 8:21 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Gary, At this juncture, I'm not getting scientific about the actual desense measurement, but I can tell you it's in the ten's of dBs. At this point, I'm using Kevin's method. signal generator connected to the cans with the cans connected to the repeater normally. I set the signal generator to the point that the squelch breaks and turn the transmitter on manually. If the signal stays there. I'm happy (at this point). If not. I increase signal generator level until I keep the signal with the transmitter on. As I said. it's ten's of dBs at this point You're correct about where I'm connecting the dummy load. Again. I'm not using ANY antennas at this point. All testing is done into the -8920 and/or the dummy load. I'm confused about your last statement. I've not put a load at the end of the tee that feeds the feedline. If I do that, I can't feed signal to the receiver. If I take the TX line off the tee and put a dummy load there, there is no desense. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 8:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
At 10/7/2008 03:03, you wrote: With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. Make sure there's an isolator on the TX. I've seen severe desense using a perfectly good, tuned duplexer because the TX didn't like the high reactance at the notch frequency, causing a lot of broadband noise to come out of the PA. If the 8920 is full duplex, I'd try a dummy load on a coupler or sampler instead just to make sure there isn't something inside it that's generating the noise. Bob NO6B
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Just out of curiosity what power supply are you using? I've seen a fair amount of RFI from the Astron SS series.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. You lost me on that one. You're saying you're testing for desense by removing the tee from the antenna port of the duplexer, feeding the Tx leg of the duplexer into a dummy load, and the Rx leg gets fed by your 8920 sig gen? If that's the case, then that's not much of a test since you're no longer duplexing. You've totally isolated the Tx and Rx, so all you really know is whether or not you have in-cabinet desense (i.e. between the transmitter and receiver internally due to poor shielding or cable cross-coupling). Or maybe I'm totally misunderstanding how you're doing the desense test - if I have, please re-explain. The easiest way to do the desense test (while keeping the feedline and antenna out of the equation) is to connect the duplexer antenna port to a high-quality (low-noise) dummy load, with an iso-tee inline between the duplexer and load. Connect your 8920 sig gen to the decoupled port on the iso-tee, generate a weak signal while monitoring the repeater Rx local receiver, and key the transmitter on and off manually. If you have desense at that point, and it sounds ratty as if something is breaking down or making intermittant contact, then go do your tappin' n' wigglin' to see if you can narrow down the list of suspects. The dummy load on the 8920 RF port is OK, but I'd still be more comfortable using a good external load and isotee. Intermittant desense can sometimes be traced back to a component or solder joint in the transmitter being defective, which can manifest as arcing (however microscopic). The resulting transmitter noise may not be easily discernable on a spectrum analyzer, especially without attenuation of the carrier frequency to increase the dynamic range of the test equipment, but may still cause appreciable desense due to the broadband noise falling on the Rx frequency. Yes, half of the duplexer's job is to attenuate transmitter noise to keep it from getting to the receiver, but if a failing component causes the effective noise level to be elevated 20 or 30 dB, that's 20 or 30 dB more isolation your duplexer would need to provide to prevent desense, and often that kind of headroom doesn't exist. Have you measured the isolation of your duplexer from Tx port to Rx port with the antenna port terminated in a dummy load? What is the measured isolation at the Tx and Rx frequencies doing this test? --- Jeff WN3A
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Jeff, I have been watching this thread and must say your explanation here is very well done. Thank you from the rest of us watching. Collin -Original Message- From: Jeff DePolo [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wed, 8 Oct 2008 1:00 pm Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. You lost me on that one. You're saying you're testing for desense by removing the tee from the antenna port of the duplexer, feeding the Tx leg of the duplexer into a dummy load, and the Rx leg gets fed by your 8920 sig gen? If that's the case, then that's not much of a test since you're no longer duplexing. You've totally isolated the Tx and Rx, so all you really know is whether or not you have in-cabinet desense (i.e. between the transmitter and receiver internally due to poor shielding or cable cross-coupling). Or maybe I'm totally misunderstanding how you're doing the desense test - if I have, please re-explain. The easiest way to do the desense test (while keeping the feedline and antenna out of the equation) is to connect the duplexer antenna port to a high-quality (low-noise) dummy load, with an iso-tee inline between the duplexer and load. Connect your 8920 sig gen to the decoupled port on the iso-tee, generate a weak signal while monitoring the repeater Rx local receiver, and key the transmitter on and off manually. If you have desense at that point, and it sounds ratty as if something is breaking down or making intermittant contact, then go do your tappin' n' wigglin' to see if you can narrow down the list of suspects. The dummy load on the 8920 RF port is OK, but I'd still be more comfortable using a good external load and isotee. Intermittant desense can sometimes be traced back to a component or solder joint in the transmitter being defective, which can manifest as arcing (however microscopic). The resulting transmitter noise may not be easily discernable on a spectrum analyzer, especially without attenuation of the carrier frequency to increase the dynamic range of the test equipment, but may still cause appreciable desense due to the broadband noise falling on the Rx frequency. Yes, half of the duplexer's job is to attenuate transmitter noise to keep it from getting to the receiver, but if a failing component causes the effective noise level to be elevated 20 or 30 dB, that's 20 or 30 dB more isolation your duplexer would need to provide to prevent desense, and often that kind of headroom doesn't exist. Have you measured the isolation of your duplexer from Tx port to Rx port with the antenna port terminated in a dummy load? What is the measured isolation at the Tx and Rx frequencies doing this test? --- Jeff WN3A
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
It's an analog supply built into the repeater. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Wednesday, October 08, 2008 11:55 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Just out of curiosity what power supply are you using? I've seen a fair amount of RFI from the Astron SS series. image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Tuesday, October 07, 2008 6:03 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, I can hear the fingerstock scraping against the inner tube... not a BAD scraping... just what sounds like good metal-to-metal contact. That is normal. The reason I asked is mine had stopped making that noise. It was almost completely silent when I rotated the knobs. That was one of the major things that led me to conclude something was really wrong inside. I knew silence when being tuned wasn't normal for those cans. After being refurbished it is back to making a healthy scraping sound. I was also thinking about cleaning the mating surfaces on the top... just need to get the gumption to do it. I'm getting tired of having my butt kicked! I know that feeling! I cleaned *every* mating surface while I had them apart, corrected some manufacturing sloppiness, and made a minor modification (which, I'm sure, was totally unnecessary, but I wasn't leaving any stone unturned). Good luck! 73, Paul N1BUG image001.jpgimage002.jpg
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes… looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white ‘stuff’ growing in there… have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed… a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is… which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Paul, I just noticed that what I wrote here was backwards... the 004s had the strap all the way around and the 005s had the wire extension. If I figure out what goes where, I'll let you know. Did you have trouble with the top of the inner loop catching on the fingerstock and tweaking it a bit? I bent a couple of mine, but it tweaked back into place okay. Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Forgot to mention... yes, the knobs were soldered on. I'm amazed they take that much heat without damage. I'm glad you figured that part out... it had me stumped. I'll report back with progress when I get them done. 73, Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
These babies are looking pretty rough, Paul (et al). After one pass with the synthetic steel wool and a wipe with isopropyl alcohol, I can see that the copper plating near the open end of the outer tubes is nearly gone on two of the cans. Have not done the other two yet, but they seem to be in better shape. I'm thinking more and more they're gonna need a refurb, although I can't see how they'd do anything with these, since the don't come apart any further. Anybody ever done a refurb from dbSpectra? Wish they'd return my calls/emails. Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Wednesday, October 08, 2008 6:27 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, Thanks for this information. I will make a note of this. The DB4060 and 4062 duplexers I've seen had identical loops (all strap) throughout. Apparently some were different for whatever reason. Here's another interesting bit... mine all had 004 penciled on them but they were built like your 005's... strap all the way around the loop. Were your knobs also soldered on? Fun, aren't they... Good luck with the cleaning. Hopefully it will help! 73, Paul N1BUG Mike Besemer (WM4B) wrote: Paul, I got the knobs off two of them and got them totally pulled apart. Both of them have a lot of lubricant on the inner tubes. looks like somebody may have lubed the threads with 3-in-1 oil or something and it ran inside. The inside of the outer tube on one of them has some white 'stuff' growing in there. have not examined it yet. The most interesting thing I noticed is that the notch filters are different. Two of them have the number 004 penciled on the bottom of the enclosure and the other two are marked 005. The ones marked 005 are copper strip all the way around the loop. On the ones marked 004, the strip stops an inch or so from the notch capacitor and has a wire connecting the cap to the strap. The way they were arranged in my setup was mixed. a 004 and a 005 on the TX and the same on the RX. I assume that was part of the problem. The question is. which goes where? I guess trial and error might solve the problem. Yahoo! Groups Links
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs.
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike Besemer (WM4B) wrote: I have a strange feeling that it’s arching around the fingerstock. The inner tuning tubes showed definite signs of wear, but I THOUGHT the fingerstock was making good contact. Is there any ‘approved’ conductive lubricant for that area? Your problem sounds a lot like the trouble I was having with my DB4062 (the 6 cavity version of the 4060). I would get it tuned and think all was well, only to have major desense the next day. It nearly drove me nuts! What happens desense-wise if you tap lightly on the big tuning knobs while the transmitter is running? Do the cans make a nice scraping sound when you turn the knobs during tune up? Mine had the moving part of the center conductor and the finger stock coated with some kind of lubricant, which had partially dried up and was interfering with contact. Check the coil springs around the finger stock to make sure they are applying adequate pressure and are not stretched out. I also recommend you check and clean EVERY metal to metal mating surface, including where the box containing the coupling loop bolts to the cavity top. I wrote up something (incomplete) on my restoration project, which can be found here: http://www.repeater.n1bug.com/duplexerrefurb.html I think Mike Morris was going to put this on the repeater-builder site, but I don't see it there yet or I'd have given that link instead. (Mike Morris: I can supply a version of this minus the DHTML menu etc. if you want it) Almost one year since the restoration now and all's well... 73, Paul N1BUG Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs. image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
No worries, Eric. I'm not giving up yet! I just want to be able to offer the answer to the inevitable 'worst case scenario' question. I definitely agree with you though. I'm a newbie to repeater stuff, but I've been juggling electrons for a long time and know that sometimes you've got to walk away for a while and get a new perspective. Having this mailing list is a huge advantage to guys like me who are just trying to 'get it done' to keep the membership happy! As always, I appreciate you (and everyone else's) advice. I've learned a lot just lurking on the list and even more when I took on the project of building this 'Frankenrepeater' project. I'm definitely just about out of ideas though. read all I can find here, on the website, and everyplace else I can think of and am running out of ideas. I guess I need to take the cans apart and inspect them again and also swap in the spare notch capacitors. but beyond that I'm getting to be at a loss! 73, Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Eric Lemmon Sent: Monday, October 06, 2008 10:50 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, I urge you to avoid jumping to any conclusions, before you determine the cause of the problem. With all due respect, I think it is premature to condemn any component of your repeater until you have performed a very thorough and intelligent investigation. The worst thing you can do, in my opinion, is rush to a conclusion simply because non-technical people want an immediate answer. Tell 'em to wait! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I've got a club meeting Thursday and need to present something to the club. Assuming worse case that the cans I have are a total loss, what suggestions have ya'll got for a replacement, assuming a 30 watt transmitter (our old reliable Mark 4). Does anybody offer a discount to hams? Any reasonable chance of getting the cans I've got repaired? Mike WM4B image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Paul, I've been thinking the same thing. I hate to tear them apart again, but I want to clean the metal-to-metal surfaces again. I can hear the fingerstock scraping against the inner tube... not a BAD scraping... just what sounds like good metal-to-metal contact. I was also thinking about cleaning the mating surfaces on the top... just need to get the gumption to do it. I'm getting tired of having my butt kicked! Thanks es 73, Mike WM4B -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Paul N1BUG Sent: Tuesday, October 07, 2008 6:58 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike Besemer (WM4B) wrote: I have a strange feeling that it's arching around the fingerstock. The inner tuning tubes showed definite signs of wear, but I THOUGHT the fingerstock was making good contact. Is there any 'approved' conductive lubricant for that area? Your problem sounds a lot like the trouble I was having with my DB4062 (the 6 cavity version of the 4060). I would get it tuned and think all was well, only to have major desense the next day. It nearly drove me nuts! What happens desense-wise if you tap lightly on the big tuning knobs while the transmitter is running? Do the cans make a nice scraping sound when you turn the knobs during tune up? Mine had the moving part of the center conductor and the finger stock coated with some kind of lubricant, which had partially dried up and was interfering with contact. Check the coil springs around the finger stock to make sure they are applying adequate pressure and are not stretched out. I also recommend you check and clean EVERY metal to metal mating surface, including where the box containing the coupling loop bolts to the cavity top. I wrote up something (incomplete) on my restoration project, which can be found here: http://www.repeater.n1bug.com/duplexerrefurb.html I think Mike Morris was going to put this on the repeater-builder site, but I don't see it there yet or I'd have given that link instead. (Mike Morris: I can supply a version of this minus the DHTML menu etc. if you want it) Almost one year since the restoration now and all's well... 73, Paul N1BUG Yahoo! Groups Links
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I've never worked with cans or repeaters, but I've witnessed similar issues caused by oxidation/corrosion. Have you tried using a conductive grease on the housing joints and the rods? It appears silver-based grease is suggested for all applications above 50 mhz. Good luck! Jacob Suter (unlicensed newb) From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Okay. I got the cable dilemma sorted out thanks to some photos I'd taken earlier, but I CANNOT get the desense out of these things. Some history: The cans and the repeater were both in storage for several years. We got a 'too good to be true' deal on the site and I pulled everything out of storage. The repeater (Mark 4) and cans were both originally on 146.85. The repeater was brought back to life on 145.11 and I tuned the cans using an HP-8920A. When I was done, I had no detectable desense either into the -8920A or at the site. Fast forward 2 months. The repeater goes deaf. I make a trip to the site (about 40 minutes) and find terrible desense. I blamed the service technician who'd just installed a new repeater for the BoE at the site, tweaked up the cans and everything was fine. for about a day. The repeater sounded great and the sensitivity was fine, but it had a terrible noise on transmit after it had been at rest for a while. About 2 minutes of RF would clean it up and it would work fine until it rested again for about 40 minutes. then it all started over again. The noise was only when the squelch was open. ID's and announcements were fine. (AH-HA!) I finally got a chance to make the trip back to the site and pulled everything home with me. I took a look at the repeater, just to give it a clean bill of health. It all looked good. I made only a few minor tweaks. The cans were noisy. I could turn the bandpass screws and I'd get noise on the receiver. That's what led me to pull the cans apart (below) to inspect and clean. There was some growth on the copper further up the outer tube, but nothing by the fingerstock. I have it a nice vinegar bath and cleaned it with a paint roller stuck inside the outer tube. It cleaned up nicely and I gave it a nice bath with the garden hose and baked the whole thing in the oven until it was good and dry. The entire process was repeated for each can. The enclosure with the notch capacitor was removed for this process, and the tuning rod screws were removed from the top to let the tuning rod drop down so I could get into the outer tube. After I put it all back together, I checked the fingerstock and it all looked good. Initial tuneup with the HP-8920 went fine and I soon had the repeater running through the cans into the -8920, breaking the squelch at about -116 dB with no detectable desense. Then. I went to bed. The next day, the desense was back with a vengeance. Been tuning for 2 days now (I thought I found it last night when I found a connector spinning on one of the cables going to the T-connector) and I CANNOT get rid of it. Sometimes it sounds like an AM radio driving under a power line. sometimes it just crackles. It's got to be microarcing somewhere, but I HATE taking those cavities apart again. (BTW, the cable with the spinning connector was replaced with good, MILSPEC RG-214 and MILSPEC connectors.) Have I missed anything? I'm really starting to think that these things are beyond salvage, but I sure hate to break that news to the club! Help! 73, Mike WM4B
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, I can hear the fingerstock scraping against the inner tube... not a BAD scraping... just what sounds like good metal-to-metal contact. That is normal. The reason I asked is mine had stopped making that noise. It was almost completely silent when I rotated the knobs. That was one of the major things that led me to conclude something was really wrong inside. I knew silence when being tuned wasn't normal for those cans. After being refurbished it is back to making a healthy scraping sound. I was also thinking about cleaning the mating surfaces on the top... just need to get the gumption to do it. I'm getting tired of having my butt kicked! I know that feeling! I cleaned *every* mating surface while I had them apart, corrected some manufacturing sloppiness, and made a minor modification (which, I'm sure, was totally unnecessary, but I wasn't leaving any stone unturned). Good luck! 73, Paul N1BUG
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
While we are on the subject of the DB4060/62, I've got a couple of dead cans with a bad tuning cap. Does anyone have a source I can call to buy some of the Johanson 5602 tuning caps? Some of the Johanson distributors don't stock it and require a big min order. I've looked at Nebraska Surplus and they have some that might work, but I'd like to find the exact replacement if possible. Thanks, Ralph W4XE
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Gary, At this juncture, I'm not getting scientific about the actual desense measurement, but I can tell you it's in the ten's of dBs. At this point, I'm using Kevin's method. signal generator connected to the cans with the cans connected to the repeater normally. I set the signal generator to the point that the squelch breaks and turn the transmitter on manually. If the signal stays there. I'm happy (at this point). If not. I increase signal generator level until I keep the signal with the transmitter on. As I said. it's ten's of dBs at this point You're correct about where I'm connecting the dummy load. Again. I'm not using ANY antennas at this point. All testing is done into the -8920 and/or the dummy load. I'm confused about your last statement. I've not put a load at the end of the tee that feeds the feedline. If I do that, I can't feed signal to the receiver. If I take the TX line off the tee and put a dummy load there, there is no desense. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 8:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs. image001.jpgimage002.jpg
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Hi Mike, I am a little confused as to how you are coupling the signal generator to the receiver. When you have the tx and rx connected to the duplexer normally and a dummy load on the output T (that would normally feed the antenna line) how are you coupling the signal generator to the receiver? Are you using an isolated T in the receive line to couple the generator in? 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 8:21 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Gary, At this juncture, I'm not getting scientific about the actual desense measurement, but I can tell you it's in the ten's of dBs. At this point, I'm using Kevin's method. signal generator connected to the cans with the cans connected to the repeater normally. I set the signal generator to the point that the squelch breaks and turn the transmitter on manually. If the signal stays there. I'm happy (at this point). If not. I increase signal generator level until I keep the signal with the transmitter on. As I said. it's ten's of dBs at this point You're correct about where I'm connecting the dummy load. Again. I'm not using ANY antennas at this point. All testing is done into the -8920 and/or the dummy load. I'm confused about your last statement. I've not put a load at the end of the tee that feeds the feedline. If I do that, I can't feed signal to the receiver. If I take the TX line off the tee and put a dummy load there, there is no desense. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Schafer Sent: Tuesday, October 07, 2008 8:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Mike, How are you measuring the desense? How are you connecting the signal generator to the receiver? What are you using for an indicator of sensitivity on the receiver, sinad, quieting etc? I am assuming that you are replacing the antenna line with a dummy load at the output junction on the duplexer when you say that you tried a dummy load on the system and you get no desense that way. Have you also tried with the antenna still connected to the output of the duplexer and the dummy load connected to the receiver input (receiver disconnected from the duplexer)? If you have no desense with a dummy load on the output of the duplexer then you do not have a duplexer problem. Let us know how you have done the above. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Tuesday, October 07, 2008 5:03 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables With the tee connector split and the TX side going into a dummy load, there is no desense. If I reconnect the tee and go to the -8920, the desense is back. The tee's are MILSPEC connectors. same ones that have always been on there. Unless something catastrophic happened, I don't THINK any of them are bad. Thanks for the suggestions though. I'm running on empty. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of DCFluX Sent: Tuesday, October 07, 2008 2:21 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I don't know if you have tried this or not, but do you have desense with the duplexer into a dummy load? Or does it just show up when you hook up an antenna? Switch mode power supplies are famous for putting out noise on 600kHz, such as found in battery chargers in boats and RVs. We recently had a problem in the area with 'The Beast' desenseing a .94 box. It turned out to be the site owners son's electric shaver charger. If this is true you only get desense when the repeater is transmitting, but it will appear on both the + and - offsets. To find the source of the problem walk around the area with an AM radio on 600kHz, or some fox hunting gear on the repeaters input. Turn down the power output of the repeater so you don't false the hand held but still have desense. Other things to look at: If I remember right this cavity has removable loops, check the solder joints between the connector and the loop and the loop to the capacitor. Your tee's may also hold some truth to the mystery, If you can not verify whom manufactured them you may wish to examine one by cutting it open with a dremmel. Some times people 'borrow' a good connector or tee and replace it with el-cheapo trucker's choice made in china goodness, of which you cut open and find steel springs.
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Have you look at your transmitter when the desense starts? David -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Okay. I got the cable dilemma sorted out thanks to some photos I'd taken earlier, but I CANNOT get the desense out of these things. Some history: The cans and the repeater were both in storage for several years. We got a 'too good to be true' deal on the site and I pulled everything out of storage. The repeater (Mark 4) and cans were both originally on 146.85. The repeater was brought back to life on 145.11 and I tuned the cans using an HP-8920A. When I was done, I had no detectable desense either into the -8920A or at the site. Fast forward 2 months. The repeater goes deaf. I make a trip to the site (about 40 minutes) and find terrible desense. I blamed the service technician who'd just installed a new repeater for the BoE at the site, tweaked up the cans and everything was fine. for about a day. The repeater sounded great and the sensitivity was fine, but it had a terrible noise on transmit after it had been at rest for a while. About 2 minutes of RF would clean it up and it would work fine until it rested again for about 40 minutes. then it all started over again. The noise was only when the squelch was open. ID's and announcements were fine. (AH-HA!) I finally got a chance to make the trip back to the site and pulled everything home with me. I took a look at the repeater, just to give it a clean bill of health. It all looked good. I made only a few minor tweaks. The cans were noisy. I could turn the bandpass screws and I'd get noise on the receiver. That's what led me to pull the cans apart (below) to inspect and clean. There was some growth on the copper further up the outer tube, but nothing by the fingerstock. I have it a nice vinegar bath and cleaned it with a paint roller stuck inside the outer tube. It cleaned up nicely and I gave it a nice bath with the garden hose and baked the whole thing in the oven until it was good and dry. The entire process was repeated for each can. The enclosure with the notch capacitor was removed for this process, and the tuning rod screws were removed from the top to let the tuning rod drop down so I could get into the outer tube. After I put it all back together, I checked the fingerstock and it all looked good. Initial tuneup with the HP-8920 went fine and I soon had the repeater running through the cans into the -8920, breaking the squelch at about -116 dB with no detectable desense. Then. I went to bed. The next day, the desense was back with a vengeance. Been tuning for 2 days now (I thought I found it last night when I found a connector spinning on one of the cables going to the T-connector) and I CANNOT get rid of it. Sometimes it sounds like an AM radio driving under a power line. sometimes it just crackles. It's got to be microarcing somewhere, but I HATE taking those cavities apart again. (BTW, the cable with the spinning connector was replaced with good, MILSPEC RG-214 and MILSPEC connectors.) Have I missed anything? I'm really starting to think that these things are beyond salvage, but I sure hate to break that news to the club! Help! 73, Mike WM4B _ From: Mike Besemer (WM4B) [mailto:mwbesemer@ mailto:[EMAIL PROTECTED] cox.net] Sent: Sunday, October 05, 2008 9:10 PM To: 'Repeater-Builder@yahoogroups.com' Subject: DB4060 Duplexer Cables I spent the weekend working on a set of DB4060 cans (cleaning and retuning) and have managed to commit the ultimate stupidity. I had all the harnesses off and instead of MARKING them I just laid them out on the bench. Unfortunately, the bench got 'cleaned' and the cables are now all mixed up. I can tell which 2 cables went between the cans and which went to the T-connector, but all 4-cables are different lengths. I assume that the shorter of the two cables go on the TX (high) side of the cans and the shorter go on the RX (low) side of the cans. Am I correct? Thanks for the help. next time I'll mark the cables! 73, Mike WM4B
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
David, Not sure what you're asking, but if you're asking about spurs, she's a clean as a whistle. VSWR is fine as well. Mike From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of David Murman Sent: Monday, October 06, 2008 8:51 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Have you look at your transmitter when the desense starts? David -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Okay. I got the cable dilemma sorted out thanks to some photos I'd taken earlier, but I CANNOT get the desense out of these things. Some history: The cans and the repeater were both in storage for several years. We got a 'too good to be true' deal on the site and I pulled everything out of storage. The repeater (Mark 4) and cans were both originally on 146.85. The repeater was brought back to life on 145.11 and I tuned the cans using an HP-8920A. When I was done, I had no detectable desense either into the -8920A or at the site. Fast forward 2 months. The repeater goes deaf. I make a trip to the site (about 40 minutes) and find terrible desense. I blamed the service technician who'd just installed a new repeater for the BoE at the site, tweaked up the cans and everything was fine. for about a day. The repeater sounded great and the sensitivity was fine, but it had a terrible noise on transmit after it had been at rest for a while. About 2 minutes of RF would clean it up and it would work fine until it rested again for about 40 minutes. then it all started over again. The noise was only when the squelch was open. ID's and announcements were fine. (AH-HA!) I finally got a chance to make the trip back to the site and pulled everything home with me. I took a look at the repeater, just to give it a clean bill of health. It all looked good. I made only a few minor tweaks. The cans were noisy. I could turn the bandpass screws and I'd get noise on the receiver. That's what led me to pull the cans apart (below) to inspect and clean. There was some growth on the copper further up the outer tube, but nothing by the fingerstock. I have it a nice vinegar bath and cleaned it with a paint roller stuck inside the outer tube. It cleaned up nicely and I gave it a nice bath with the garden hose and baked the whole thing in the oven until it was good and dry. The entire process was repeated for each can. The enclosure with the notch capacitor was removed for this process, and the tuning rod screws were removed from the top to let the tuning rod drop down so I could get into the outer tube. After I put it all back together, I checked the fingerstock and it all looked good. Initial tuneup with the HP-8920 went fine and I soon had the repeater running through the cans into the -8920, breaking the squelch at about -116 dB with no detectable desense. Then. I went to bed. The next day, the desense was back with a vengeance. Been tuning for 2 days now (I thought I found it last night when I found a connector spinning on one of the cables going to the T-connector) and I CANNOT get rid of it. Sometimes it sounds like an AM radio driving under a power line. sometimes it just crackles. It's got to be microarcing somewhere, but I HATE taking those cavities apart again. (BTW, the cable with the spinning connector was replaced with good, MILSPEC RG-214 and MILSPEC connectors.) Have I missed anything? I'm really starting to think that these things are beyond salvage, but I sure hate to break that news to the club! Help! 73, Mike WM4B _ From: Mike Besemer (WM4B) [mailto:[EMAIL PROTECTED] Sent: Sunday, October 05, 2008 9:10 PM To: 'Repeater-Builder@yahoogroups.com' Subject: DB4060 Duplexer Cables I spent the weekend working on a set of DB4060 cans (cleaning and retuning) and have managed to commit the ultimate stupidity. I had all the harnesses off and instead of MARKING them I just laid them out on the bench. Unfortunately, the bench got 'cleaned' and the cables are now all mixed up. I can tell which 2 cables went between the cans and which went to the T-connector, but all 4-cables are different lengths. I assume that the shorter of the two cables go on the TX (high) side of the cans and the shorter go on the RX (low) side of the cans. Am I correct? Thanks for the help. next time I'll mark the cables! 73, Mike WM4B
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I neglected to mention in the first post, but I also put the crystals into a 2nd repeater we have and had the same problem. I may have to try tuning the cans on our spare 6.85 machine. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 8:56 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables David, Not sure what youre asking, but if youre asking about spurs, shes a clean as a whistle. VSWR is fine as well. Mike From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of David Murman Sent: Monday, October 06, 2008 8:51 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Have you look at your transmitter when the desense starts? David -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Okay I got the cable dilemma sorted out thanks to some photos Id taken earlier, but I CANNOT get the desense out of these things. Some history: The cans and the repeater were both in storage for several years. We got a too good to be true deal on the site and I pulled everything out of storage. The repeater (Mark 4) and cans were both originally on 146.85. The repeater was brought back to life on 145.11 and I tuned the cans using an HP-8920A. When I was done, I had no detectable desense either into the -8920A or at the site. Fast forward 2 months. The repeater goes deaf. I make a trip to the site (about 40 minutes) and find terrible desense. I blamed the service technician whod just installed a new repeater for the BoE at the site, tweaked up the cans and everything was fine for about a day. The repeater sounded great and the sensitivity was fine, but it had a terrible noise on transmit after it had been at rest for a while. About 2 minutes of RF would clean it up and it would work fine until it rested again for about 40 minutes then it all started over again. The noise was only when the squelch was open IDs and announcements were fine. (AH-HA!) I finally got a chance to make the trip back to the site and pulled everything home with me. I took a look at the repeater, just to give it a clean bill of health. It all looked good I made only a few minor tweaks. The cans were noisy. I could turn the bandpass screws and Id get noise on the receiver. Thats what led me to pull the cans apart (below) to inspect and clean. There was some growth on the copper further up the outer tube, but nothing by the fingerstock. I have it a nice vinegar bath and cleaned it with a paint roller stuck inside the outer tube. It cleaned up nicely and I gave it a nice bath with the garden hose and baked the whole thing in the oven until it was good and dry. The entire process was repeated for each can. The enclosure with the notch capacitor was removed for this process, and the tuning rod screws were removed from the top to let the tuning rod drop down so I could get into the outer tube. After I put it all back together, I checked the fingerstock and it all looked good. Initial tuneup with the HP-8920 went fine and I soon had the repeater running through the cans into the -8920, breaking the squelch at about -116 dB with no detectable desense. Then I went to bed. The next day, the desense was back with a vengeance. Been tuning for 2 days now (I thought I found it last night when I found a connector spinning on one of the cables going to the T-connector) and I CANNOT get rid of it. Sometimes it sounds like an AM radio driving under a power line sometimes it just crackles. Its got to be microarcing somewhere, but I HATE taking those cavities apart again. (BTW, the cable with the spinning connector was replaced with good, MILSPEC RG-214 and MILSPEC connectors.) Have I missed anything? Im really starting to think that these things are beyond salvage, but I sure hate to break that news to the club! Help! 73, Mike WM4B _ From: Mike Besemer (WM4B) [mailto:[EMAIL PROTECTED] Sent: Sunday, October 05, 2008 9:10 PM To: 'Repeater-Builder@yahoogroups.com' Subject: DB4060 Duplexer Cables I spent the weekend working on a set of DB4060 cans (cleaning and retuning) and have managed to commit the ultimate stupidity. I had all the harnesses off and instead of MARKING them I just laid them out on the bench. Unfortunately, the bench got cleaned and the cables are now all mixed up. I can tell which 2 cables went between the cans and which went to the T-connector, but all 4-cables are different lengths. I assume
Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Sounds like maybe a bad notch cap or a bad harness cable. At first I thought maybe a transmitter spur, but you've now ruled that out. Neither may show up on your HP, but under real power it could. Chuck WB2EDV - Original Message - From: Mike Besemer (WM4B) [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, October 06, 2008 9:04 PM Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I neglected to mention in the first post, but I also put the crystals into a 2nd repeater we have and had the same problem. I may have to try tuning the cans on our spare 6.85 machine. Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 8:56 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables David, Not sure what you're asking, but if you're asking about spurs, she's a clean as a whistle. VSWR is fine as well. Mike
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I don't THINK it's a cable. no amount of beating, poking, or flexing seems to make any difference. I've thought about the notch caps. I do have a couple of spares. maybe I'll try to swap them in. The question is. WHICH TWO? I've swapped TX and RX sides of the duplexers already with no effect. You'd think that the notch caps on the RX side would be the ones that'd cause the most grief, but I can see how the others would too. Either way, I'd have expected to see some difference when I swapped TX and RX sides. I have a strange feeling that it's arching around the fingerstock. The inner tuning tubes showed definite signs of wear, but I THOUGHT the fingerstock was making good contact. Is there any 'approved' conductive lubricant for that area? Mike WM4B _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Kelsey Sent: Monday, October 06, 2008 9:15 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Sounds like maybe a bad notch cap or a bad harness cable. At first I thought maybe a transmitter spur, but you've now ruled that out. Neither may show up on your HP, but under real power it could. Chuck WB2EDV - Original Message - From: Mike Besemer (WM4B) [EMAIL PROTECTED] mailto:mwbesemer%40cox.net net To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Sent: Monday, October 06, 2008 9:04 PM Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I neglected to mention in the first post, but I also put the crystals into a 2nd repeater we have and had the same problem. I may have to try tuning the cans on our spare 6.85 machine. Mike WM4B From: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com [mailto:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 8:56 PM To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables David, Not sure what you're asking, but if you're asking about spurs, she's a clean as a whistle. VSWR is fine as well. Mike
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
I've got a club meeting Thursday and need to present something to the club. Assuming worse case that the cans I have are a total loss, what suggestions have ya'll got for a replacement, assuming a 30 watt transmitter (our old reliable Mark 4). Does anybody offer a discount to hams? Any reasonable chance of getting the cans I've got repaired? Mike WM4B _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Kelsey Sent: Monday, October 06, 2008 9:15 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Sounds like maybe a bad notch cap or a bad harness cable. At first I thought maybe a transmitter spur, but you've now ruled that out. Neither may show up on your HP, but under real power it could. Chuck WB2EDV - Original Message - From: Mike Besemer (WM4B) [EMAIL PROTECTED] mailto:mwbesemer%40cox.net net To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Sent: Monday, October 06, 2008 9:04 PM Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I neglected to mention in the first post, but I also put the crystals into a 2nd repeater we have and had the same problem. I may have to try tuning the cans on our spare 6.85 machine. Mike WM4B From: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com [mailto:Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 8:56 PM To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables David, Not sure what you're asking, but if you're asking about spurs, she's a clean as a whistle. VSWR is fine as well. Mike
RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables
Mike, I urge you to avoid jumping to any conclusions, before you determine the cause of the problem. With all due respect, I think it is premature to condemn any component of your repeater until you have performed a very thorough and intelligent investigation. The worst thing you can do, in my opinion, is rush to a conclusion simply because non-technical people want an immediate answer. Tell 'em to wait! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Besemer (WM4B) Sent: Monday, October 06, 2008 7:39 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Desense has me pulling my hair out! (Was DB4060 Duplexer Cables I've got a club meeting Thursday and need to present something to the club. Assuming worse case that the cans I have are a total loss, what suggestions have ya'll got for a replacement, assuming a 30 watt transmitter (our old reliable Mark 4). Does anybody offer a discount to hams? Any reasonable chance of getting the cans I've got repaired? Mike WM4B
